Materials science
Honeycomb-like structure thwarts a projectile travelling as fast as a speeding bullet.
A carbon sheet that is no thicker than a human hair can withstand the impact of minuscule ‘bullets’ that hurtle towards it at twice the speed of sound.
Researchers are keen to find materials that can take hits from objects such as rogue shrapnel and space debris. Carlos Portela at the Massachusetts Institute of Technology in Cambridge, Julia Greer at the California Institute of Technology in Pasadena and their colleagues designed a lattice, not unlike a 3D honeycomb, whose individual cells have 14 sides. They used 3D printing to precisely construct the lattice from a flexible polymer and heated it until only pure carbon remained.
The researchers fired spheres resembling sand particles, only a few micrometres in diameter, at the material. At lower speeds, the spheres simply bounced off the lattice. But at higher speeds, they gouged out neat ‘craters’ and crushed the lattice underneath while remaining lodged in the pits, rather than piercing the material.
By adjusting a model that describes cratering by meteors, the researchers could predict crater formation in their materials. They hope their model can inform other lightweight, blast-proof designs.
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